Organic Cu-complexation at the shallow marine hydrothermal vent fields off the coast of Milos (Greece), Dominica (Lesser Antilles) and the Bay of Plenty (New Zealand)

Assuming that the three investigated sites are representative for shallow marine hydrothermal vents, the Cu-flux into the ocean due to complexation appears to be relatively low compared to deep-sea systems. Our data indicate a stable complexation of Cu in most cases, which may lower the toxic effect of Cu on these mixed photic-chemosynthetic communities. However one pore water sample from Dominica showed an excess [Cu]T over [L]Cu, which would create a highly toxic environment for most marine organisms. We further show that ligand-Cu ratios and complex stability constants are in a similar range as the ones at deep-sea vents, which may indicate similar complexation parameters and processes at shallow and deep-sea hydrothermal vents.